Combination snap action push-pull switch and variable resistor



July 22, 1958 w. A. BARDEN AL 2,844,676

y COMBINATION SNAP ACTION P 'L SWITCH AND VARIABLE ISI Filed July 1956 l5%91 82 v 30 '57 35 l C 4k. i l ar-'I 2 '7 2% 7 z? Agi? wggllll QI 55MJAM W l 47 Wayne AEa'rdez-z United States Patent COMBINATION SNAPACTION PUSH-PULL SWITCH AND VARIABLE RESISTOR Wayne A. Barden, Elkhart,and Donald A. Pierce, South Bend, Ind., assignors to Chicago TelephoneSupply Corporation, Elkhart, Ind., a corporation of Indiana ApplicationJuly 30, 1956, Serial No. 601,059

3 Claims. (Cl. Zim- 67) This invention relates to electrical controlinstrumentalities and has more particular reference to a tandem mountedcombination variable resistor and electric switch of the type suitablefor use in radio and television receivers. In general, it is the purposeof this invention to provide a combination electrical controlinstrumentality of this type wherein the switch may be operated withoutdisturbing the setting of the Variable resistor.

In the conventional combination on-olf switch and volume control used onradio and television receivers, rotation of a common drive shaft for theunit effects actuation of both the switch and the variable resistor.Hence, with this conventional arrangement, the switch cannot be actuatedto the olf position without adjusting the volume to its lowest setting,and each time the receiver is turned on the operator must patiently waitthrough a rather lengthy warm-up period before the volume can bere-adjusted to the desired level.

In the past some effort has been made to correct this undesirablesituation through the provision of a cornbination switch and variableresistor wherein rotation of a single operating shaft effectedadjustment of the variable resistor and axial motion of the shafteifected switch actuation without disturbing the setting of the variableresistor. However, the switch components of such switch and variableresistor combinations have not only lacked the positive snap actiondesired in electric switches, but they have been excessively spaceconsuming and bulky because they merely combined a variable resistorwith a conventional rotary type switch having its parts reoriented sothat the switch arm moved edgewise in a plane parallel to the axis ofthe common actuating shaft of the combination. This reorientation wasone of the lirst and most obvious solutions to the problem of push-pullswitch operation in a combination unit of the character described.

As 'the radio and television industry has progressed, however, manyeconomies have been effected. Significant among these economies has beenthe use of smaller, lighter and more compact parts and assemblies toconserve the amount of metal and other materials required. This progresshas made possible the mass production of small, compact, light weightand reasonably priced table model radios of good quality. Thecombination variable resistor and conventional reoriented push-pullswitch of large and bulky proportions obviously was unsuitable for suchsmall and compact table model radios. Moreover, the conventional switchcomponents of such combination units, reoriented for push-pulloperation, required a considerable amount of force for their actuation,with the result that small radios in which they were installed werefrequently moved bodily by the operator while actuating the switch.Hence such switches were entirely out of the question for light weightradios.

With these objections in mind, it is an object of this invention toprovide a simple, exceptionally compact and inexpensive combinationpush-pull switch and variable resistor which is so'designed that theswitch can be op- 2,844,67 6 Patented July 22, ,1958

ICC

erated not only without affecting the setting of the variable resistor,but with a relatively light force, so as to render the combination unitof this invention especially well suited for use on small, light weightltable model radios, as well as the larger and heavier radio andtelevision receivers.

More specifically, it is an object of this invention to provide acombination push-pull electric switch and variable resistor in which theswitch component incorporates an improved switch mechanism of theovercenter type which assures highly desirable and positive snap-actionof the mechanism, wiping engagement between its stationary and movablecontacts, and renders old space consuming reorientation of the switchparts unnecessary.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiment of thehereindisclosed invention may be made as come within the scope of theclaims.

The accompanying drawing illustrates one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

Figure l is a view partly in side elevation and partly in longitudinalsection illustrating a combined variable resistor and snap switchembodying the principles of this invention, and showing the switch inclosed position;

Figure 2 is a view similar to Figure l, but illustrating ing the switchin open position; f

Figure 3 is a cross sectional view taken through Figure 2 along theplane of the line 3 3; and

Figure 4 is a fragmentary detail view taken along the line 4 4 in Figurel.

Referring now more particularly to the accompanying drawing in whichlike numerals indicate like parts, the combination electrical controlinstrumentality of this invention comprises a variable resistor 5 and anelectric l switch 6 at the rear of the resistor, both components of theinstrumentality being actuatable by a common operating shaft 7projecting into the variable resistor from the front thereof.

Except as noted hereinafter, the variable resistor is of conventionalconstruction. It comprises a housing 8 having spaced substantiallyparallel front and rear walls 9 and l0, respectively, and a cylindricalsheet metal side wall 11 extending between and joining the front andrear walls. As shown, the rear wall may be integral with the side wall,and it is provided with a large central opening 13 therein for a purposeto be described later.

The front wall 9 of the variable resistoris provided by an insulatingbase which has the stator assembly of the resistor secured to its innerface. This stator assembly includes a conventional type of arcuatestrip-like resistance element 15 of carbonaceous material, and acollector ring 16, both surrounding and mounted coaxially with a hole 17in the center of the insulating base 9. A contact carrier 18 ofinsulating material, shown as of the molded type, is interposed betweenthe stator assembly and the rear wall 10 of the housing, and has anannular rib 19 projecting axially from its rear into engagement with therear wall 10 to define the rearmost axial position of the contactcarrier in the resistor housing. The body portion of the carrier isprovided with a central non-circular hole 20 leading entirelytherethrough so as to open to the well 21 defined by the axiallyrearwardly projecting rib 19 on the carrier.

According to this invention, the operating shaft 7 is carried by thefront wall or base 9 of the variable resistor for rotary motion aboutits longitudinal axis so as to provide for actuation of the variableresistor, and for endwise back and forth motion so as to provide foractuation of the electric switch 6. For this purpose, the shaft isfreely rotatably and slidably received in a bushing 23 having its innerend secured in the hole 17 in the base 9 and having a threaded forwardportion which provides for securement of the combined electrical controlinstrumentality to the back of a panel or the like.

The contact carrier 18 is mounted on the inner end portion of theoperating shaft and is slidably splined thereto so as to rotate with theshaft while allowing endwise sliding motion of the shaft relativethereto. For this purpose, the rear end portion of the operating shafthas Va non-circular or flattened cross section, as indicated at 25,which conforms to the shape of the non-circular hole 20 in the carrier,and by which `the shaft may be moved endwise a substantial distancerelative to the contact carrier while maintaining the latter drivinglyconnected with the shaft for rotation therewith.

It will be understood, of course, that rotation of the operating shaftis transmitted to the contact carrier 18 for the purpose of adjustingthe positions of contact fingers 26 and 27, respectively, fixed on thefront face of .the carrier, with relation to the resistance element andcollector ring and 16 upon which the fingers track; and that theabutting engagement of the annular rib 19 on the back of the carrierwith the rear wall 10 of the housing serves to hold the contact lingersengaged with the components of the stator assembly with the properdegree of spring tension.

The electric switch 6 of this invention is mounted in a housing 29mounted on the back of the resistor housing. It comprises a cylindricalsheet metal side wall 30 of substantially the same diameter as the sidewall of the resistor housing, and a rear wall 31 of insulating materialand providing a terminal head closing the back of the switch housing.The front of the side wall 30 abuts the rear wall 10 of the resistorhousing and has a plurality of circumferentially spaced ears 33projecting forwardly therefrom through slits (not shown) in the rearwall 10 of the variable resistor housing and bent over upon the forwardface of the wall 10 to secure the two housings together. The ears 33preferably hold the switch housing on the back of the resistor housingwith the rear walls of the two housings in spaced parallel relation andwith the side walls of the two housings coaxial with one another. Withthis arrangement, the interior of the switch housing is in opencommunication with the well 21 in the back of the contact carrier 1Sthrough the `large central opening 13 in the rear wall of the resistorhousing.

The housing 29 contains switch mechanism which in- Ic ludes a pair ofsubstantially flat spaced apart stationary contacts 35 overlying thefront face of the terminal head 31 and fixed thereto with terminalportions 36 thereon projecting rearwardly through suitable openings (notshown) in the terminal head. The switch mechanism also includes anelongated bridging contactor 38 having a pair of fixed contact portionsor buttons 39 on its rear surface near the opposite ends of thecontactor and each cooperable with one of the stationary contacts 35.

The bridging contactor 38 is fixed to the outer end portion of anelongated, substantially fiat switch arm 40, with an insulator 41interposed therebetween. The arm 40 substantially flatwise overlies theterminal head and extends transversely across the switch housing withthe contactor disposed at the rear of the arm. The inner end portion ofthe switch arm is bifurcated to define spaced parallel fingers 42, theextremities of which are pivotally received in transversely oppositenotches 43 in the upstanding flanges 44 of a channel-shaped actuatingmember 45. The web of the actuating member 45 faces outwardly, towardthe side wall of the switch housing,

and fiatwise seats upon the web of a channel-shaped guide member 46having flanges 47 which project upwardly therefrom and loosely embracethe flanges of the actuating member. One end of the guide member 46 isxed to the terminal head as at 49 to dispose the guide membersubstantially perpendicular to the terminal head 31 and with its web 50remote from the stationary contacts of the switch.

The guide member, therefore, not only supports the actuating member inthe switch housing, but serves to guide the actuating member for foreand aft translating motion toward and from the terminal head 31 along apath normal thereto. The notches 43 in the outer edges of the actuatingmember flanges provide a fulcrum for the bifurcated end of the switcharm 40, to enable the switch arm to tilt back and forth in the switchhousing in directions to carry the contact points 39 on the bridgingcontacter to and from engagement with the stationary contacts 35 of theswitch.

In order to assure a highly desirable snap action for the switch arm andthe maintenance of good contact pressure between the points 39 and theircooperating stationary contacts in the switch closed position, theswitch mechanism of this invention is of the overcenter type. For thispurpose, the switch mechanism is provided with a helically coiledtension spring 52, connected in overcenter relation between the switcharm 40 and a sta tionary part on the switch housing. The spring has adiameter such as to readily pass between the bifurcations 42 on theinner end of the switch arm, and one end thereof is hooked into a hole53 in the arm adjacent to the base of the bifurcations, but centrallythereof. The

, other end of the spring passes through a clearance slit 54 in the webof the actuating member 45 and engages around an anchor 55 on the web ofthe guide member 46, outwardly of the pivoted end of the switch arm.

The tension spring thus at all times exerts a force on the switch armtending to hold its pivoted end in the fulcrum defining notches 43 andto maintain the actuating member nested in its guide member. The springalso acts upon the arm to yieldingly maintain it tilted either forwardlyor rearwardly depending upon whether its fulcrum is disposed forwardlyor rearwardly of a straight line along which force is exerted on the armby the spring.

Thus, in the switch closed position shown in Figure l, the fulcrum forthe bifurcated end of the switch arm lies a short distance forwardly ofthe axis of the tension spring 52, or forwardly of the straight linealong which force is applied to the switch arm by the spring, and thelatter accordingly holds the switch arm tilted rearwardly with itscontact points 39 firmly engaged with the stationary contacts'35 on theterminal head. The switch is operated ,to the switch open position as aconsequence of forward tilting motion of the switch arm, away from theterminal head, and such actuation of the switch is effected by rearwardsliding motion of the actuating member 45 toward the terminal head adistance sufficient to carry the fulcrum for the switch arm rearwardlybeyond the straight line along which force is exerted upon the switcharm by the tension spring.

The switch open position shown in Figure 2 is defined jointly by theengagement of the rear end of the actuating member 45 with the innerface of the terminal head 31, and by the engagement of the outer endportion of the forwardly tilted switch arm with a tab 57 on the switchhousing struck inwardly from the side wall 30 thereof and lying againstthe rear wall 10 of the resistor housing. The switch closed positionshown in Figure 1 is defined jointly by the engagement of the contactpoints 39 with the stationary contacts on the terminal head, and by theengagement of a stop 59 on the actuating member with the rear wall 10 ofthe resistor housing adjacent to the edge of the large Vcentral aperture13 therein, The stop 59 is shown as being b ent radially inwardly of theswitch housing from a forward extension of the web of the actuatingmember.

One of the advantages of the switch of this invention is that itoperates with a pronounced snap action. This snap action, of course,results from the connection of the tension spring 52 between the switcharm and a stationary part on the switch housing in overcenter relationwith respect to the switch arm and the shiftable fulcrum upon which itsinner or bifurcated end portion tilts.

Another feature of the switch mechanism of this invention resides in thefact that both the make and the break of the switch are accompanied by ahighly desirable rolling and/or wiping action of the convex points 39upon the flat surfaces of the stationary contacts 35. This latterfeature results from the fact that operation of the snap switchmechanism requires forward and rearward translation of the fulcrum uponwhich the bifurcated end portion of the switch arm is supported, so thatas the fulcrum moves in either direction along a path which isperpendicular to the terminal head and the surfaces of the stationarycontact thereon, the switch arm is simultaneously shifted lengthwise andthereby caused to rock upon its Contact points when the latter areengaged with the stationary contacts.

As stated previously, the same operating shaft 7 by which the variableresistor is actuated is also relied upon to effect actuation of theswitch mechanism between its open and closed positions, but withoutnecessitating any change in the setting of the variable resistor. Forthis purpose, the rotatable and endwise slidable operating shaft 7 ofthe instrumentality is drivingly connected with the actuating member 45of the switch mechanism by means which is effective only upon back andforth endwise sliding movement of the shaft. This connection is providedby a forward and inward extension of the stop portion 59 on theactuating member, terminating in a fork-like foot or actuator 61directly behind the operating shaft. The bifurcations of the actuator 61loosely -straddle a reduced coaxial neck 62 on the rear end of the shaftand are confined between the end of the shaft and a head 63 on the rearextremity of the neck.

When the operating shaft 7 is pushed rearwardly toward and throughtheenlarged opening 13 in the rear wall of the resistor housing,therefore, it propels the actuating member 45 of the switch rearwardlywith it, through the engagement of the rear end of the shaft with theactuator 61, to the extreme of rearward motion dened by the engagementof the actuating member with the terminal head 31 of the switch housing.

During such shaft produced rearward motion of the actuating member, andsubstantially at the time the actuating member carries the pivoted endportion of the switch arm to and slightly beyond the straight line alongwhich force is exerted on the arm by the tension spring, the spring actsupon the switch arm to suddenly snap the same to its forwardly tiltedswitch open position seen in Figure 2.

Attention is directed to the fact that such operation of the switchmechanism to actuate the same to the switch open position does notentail any rotary motion of the operating shaft such as would change thesetting of the variable resistor. In a similar manner, except forforward endwise sliding motion of the operating shaft, the switch may beactuated to its closed position from the open position seen in Figure 2,without entailing any rotation of the operating shaft or alteration inthe setting of the variable resistor.

Again, during such forward endwise motion of the operating shaft fromits innermost position seen in Figure 2, the switch arm will be snappedrearwardly upon its forwardly moving fulcrum as soon as the latter iscarried to and slightly beyond the straight line along which. force isexerted upon the switch arm by the tension sprmg.

The extreme of inward endwise motion of the operating shaft may bedefined either by the engagement of the rear end of the actuating member45 of the switch with the terminal head 31 of the switch housing, asshown; or by the direct engagement of a stop, such as the rearwardly.facing shoulder 65 dened by the junction between the cylindrical andnon-circular rear end portions of the operating shaft, with the frontface of the contact carrier 18 when the shaft is in its depressedposition seen in Figure 2. In the latter event, the rearward thrust ofthe shaft would be harmlessly transmitted to the rear wall fil of theresistor housing through the contact carrier 1S.

It is important to note, however, that no forward axial force is imposedupon the Contact carrier 18 of the variable resistor during closure ofthe switch. This results from the fact that forward motion of theoperating shaft 7 necessary to close the switch is limited by theengagement of the stop 59 on the actuating member with the rear wall 10of the resistor housing. Thus, in the forward limit of motion of theoperating shaft seen in Figure 1, the non-circular rear end portion ofthe. shaft map project a Very slight distance from the body portion ofthe contact carrier and into the well 21 in its rear, while thefork-like actuator 61 with which it is connected is spaced a slightdistance rearwardly from the bottom of the well 21 in the contactcarrier.

The combination electrical instrumentality described featuressimplicity, reliable over-center snap actuation of the switch bysubstantially small forces exerted on the operating shaft, and a degreeof compactness which was previously sought but never attained incombination variable resistor and switch instrumentalities of the typeherein concerned, These features are assured partly through theprovision of a switch incorporating a switch which extends transverselyacross the interior of the switch housing and is supported on aforwardly and rearwardly shiftable fulcrum for tilting motionsubstantially flatwise toward and from the terminal head about an axiscrosswise of the operating shaft; an-d partly by having the actuator 61of the switch mechanism project through the opening 13 inthe rear wallof the resistor housing to be accommodated in a well in the rear of thecontact carrier of the resistor in the switch closed position.

From the foregoing description taken together with the accompanyingdrawing, it will be readily apparent to those skilled in the art thatthis invention provides an improved combination variable resistor andelectrical switch featuring compactness and an extremely simple andreliable snap switch mechanism which may be operated by endwise back andforth sliding motion of the common operation shaft of theinstrumentality without in anywise affecting the setting of the variableresistor.

What is claimed as our-invention is:

l. An electric snap switch comprising: a housing having a cylindricalside wall and having a substantially flat wall of insulative materialproviding a terminal head closing the rear of the housing; a pair ofstationary contacts fixed on the inner side of the terminal head andhaving forwardly facing contact surfaces transversely spaced from theside wall and from one another along substantially a diameter of thehousing so as to be located at substantially the widest part of thehousing; a T-shaped contactor in the housing having its headelectrically insulated from its stem and transversely overlying thestationary contacts, the stem of the contactor crossing the housing axisand having its base closely adjacent to the side wall of the housing; anactuating member adjacent to the base of the contactor; means on saidactuating member supporting the T-shaped contactor at itsvbase for backand forth pivotal motion about an axis parallel to the terminal head sothat the head of the contactor may be swung toward and from the terminalhead between a rearwardly tilted contact bridging position and aforwardly tilted switch open position; a spring connected in overcenterrelation between the contactor and a xed part on the housing foryieldingly holding the contactor in either its forwardly or rearwardlytilted positions; guide means fixed on the housing near the side wallthereof and supporting the actuating member for motion in oppositedirections axially of the housing to carry the pivoted base of thecontactor toward and from the ter minal head, to one side or the otherof a straight line along which biasing force is exerted on the contactorby said overcenter spring; and means on said actuating member providingan actuator adjacent to the front of the housing by which the actuatingmember may be shifted back and forth so as to effect snap actuation ofthe contactor in either direction as a consequence of shifting of saidactuating member in the opposite direction to and beyond a position atwhich the pivoted base of the contactor stem passes through said linealong which biasing force is exerted on the contactor.

2. The electric snap switch set forth in claim 1 wherein said guidemember is a channel-shaped part having one end fixed to the terminalhead, said part projecting forwardly from the terminal head and having aweb disposed close to but spaced from the housing side wall and parallelto the housing axis, and anges which face away from the hou-sing sidewall and extend axially of the housing, the actuating member restingupon the web of said channel-shaped part and being loosely embraced bythe flanges thereof so as to be guided by said channelshaped part forback and forth sliding motion in the housing.

3. In an electrical instrumentality of the character described: housingmeans providing a switch compartment having a cylindrical side wall, acentrally apertured front wall, and an end wall closing the rear of thecompartment; a pair of stationary contacts fixed on the inner side ofsaid end wall, said stationarly contacts having forwardly facing contactsurfaces thereon transversely spaced from one another and from said sidewall and located at one side of but close to a plane containing the axisof the compartment, at substantially the widest part'of the compartment;a channel-shaped guide member having one end fixed to said end wall atthe other side of and remote from said plane, said guide memberextending forwardly toward the front wall of the compartment and havinga web which is parallel to said plane, and transversely spaced axiallyextending flanges projecting toward said plane; an actuating memberloosely received in said channel-shaped member and guided thereby forback and forth sliding motion along a path parallel to the compartmentaxis, between limits dened by the engagement of said actuating memberwith the front and rear walls of the compartment; a T-shapedcontactor'having its head electrically insulated from its stem andtransversely overlying and cooperable with the stationary contacts tobridge the same, the base of said stem being located adjacent to theactuating member; means on the actuating member supporting the T-shapedcontactor at its base for bodily movement therewith and for back andforth pivotal motion relative to the actuating member about an axiscrosswise of the compartment and parallel to said plane, between arearwardly tilted contact bridging position and a forwardly tiltedswitch open position; a spring connected in overcenter relation betweenthe contactor and a part on the guide member for yieldingly holding thecontactor tilted either forwardly or rearwardly, and operable to effectsnap actuation of the contactor in either direction as a consequence ofsliding motion of the actuating member in the opposite direction to andbeyond a position intermediate its limits of motion at which the pivotedbase of the contactor passes through a straight line along which biasingforce is exerted on the contactor by said spring; and means on theactuating member providing an actuator by which the actuating member maybe shifted back and forth so as to effect snap actuation of thecontactor from one position to the other, said actuator having a portiondisposed centrally of the switch compartment, adjacent to the frontthereof, and which portion is movable outwardly ythrough the aperture inthe front wall of the compart ment to carry the actuating member to itsforward limit of motion.

References Cited in the file of this patent UNITED STATES PATENTS1,501,148 Terhorst et al July 15, 1924 1,991,113 Nette Feb. 12, 19352,015,425 Gaubert Sept. 24, 1935 2,596,893 Finizie May 13, 1952 FOREIGNPATENTS 464,406 Canada Apr. 18, 1950 814,209 France .lune 18, 1937500,522 Great Britain Feb. 10, 1939 687,420 Germany `Tan. 29, 1940703,179 Germany Feb. 24, 1941 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No, 844,676 July 22, 1958 Wayne A Barden et ala It ishereby certified that error appears in the printed specifi@ cation ofvthe above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.,

Column 2, line 34)7 strike out the syllable ning" column y line 2l, for"map" read -mmay on; line 33, after "switch", second occurrence, insertf== arm -mg column '7, line 34, for "etationarly" Signed and. sealedthis 28th day of October 195811 (SEAL) Attest:

KARL H AXLINE ROBERT C. WATSON ttesting Officer Conmissioner of PatentsUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nm,$844,676 July 22, 1958 Wayne Ata Barden et al.,

It is hereby certified that error appears in the printed specifi@-cation of the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.,

Column 2, line 34, strike out the syllable "ing" g column 6, line 2l,for "map" read nl may u; line 33, after "switch", second occurrence,vinsert ee arm n; Column 7, line 34, for Hstatonarly" read stationarySigned and sealed this 28th day of October l958 (SEAL) Attest:

KARL H.. AXLINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

